Ahead of this week's 124th U.S. Open at Pinehurst No. 2, the greens were the hot topic of the day Monday, particularly for defending champion Wyndham Clark.

Clark, who won last year at Los Angeles Country Club for his first major title, was surprised how much Pinehurst No. 2 had changed since a visit about a month earlier.

"The greens are extremely fast and penal," he told reporters after Monday's practice round. "You hit it on the green, the hole is not done. I was just amazed how fast the greens are.